1. Field of the Invention
The present invention relates to an electronic device, and a circuit and a method for protecting the same, and more particularly to a portable electronic device in which a battery is incorporated and a circuit and a method for protecting the same.
2. Description of the Related Art
Many portable electronic devices use batteries as power sources. The electronic device in which a battery is incorporated usually has a battery protection circuit. In order to prevent performance deterioration or destruction of the battery, the battery protection circuit instantaneously cuts off an excessive current when the excessive current flows out of the battery. This battery protection circuit is operated even when an excessive current flows to an electronic circuit such as a power amplifier. Thus, the battery protection circuit can prevent destruction of the electronic circuit caused by continuous flowing of an excessive current thereto in the electronic device.
A recent portable electronic device such as a cellular telephone has a large display unit, illumination, and camera functions, a vibration motor and the like. Accordingly, power consumption of the cellular telephone has increased. Since the increased power consumption needs a greater supply of a current, an operation threshold level of the battery protection circuit must be set high.
However, the high operation threshold level of the battery protection circuit causes a loss of the aforementioned function thereof to protect the electronic circuit in the electronic device. For example, a large current may flow to an electronic circuit such as a transmission power amplifier directly connected to the battery because of a control abnormality or a component abnormality. In such a case, the battery protection circuit that has the high operation threshold level cannot cut off the battery current quickly. Consequently, the amplifier is irreparably damaged. Japanese Registered Patent No. 3320486 discloses a technology for melting a fuse of an AC power source to cut off the power source when a voltage abnormality is detected in a power amplifier circuit. However, this method cannot cut off a current instantaneously.